Device for connecting and disconnecting core tubes to a trolley in concrete casting machines

ABSTRACT

From US Pat. No. 3,642,419 it is known to pervey a concrete casting machine with more core tubes than necessary for a single mold. Therefore at each casting a number of core tubes are retained, while the other core tubes are moved on a trolley towards and into the empty mold. Now the said core tubes are retained in their most retracted position by means of twin-arm levers , engaging either a fix hook in a link member connected to the core tube; this gives a reliable connecting and disconnecting possibility which is vastly automatically controlled.

United States Patent 11 1 1111- 3,829,265 Holm 1451 Aug. 13, 1974 [54]DEVICE FOR CONNECTING AND 1,977,374 10/1934 Brooke et al. 425/468DISCONNECTING C TUBES o A 3,534,450 10/1970 lpsen 425/457 TROLLEY INCONCRETE CASTING 3,642,419 2/1972 Toksvig 425/457 MACHINES PrimaryExaminer-Robert D. Baldwin lmemori ig ls Holm, Hellerup, AssistantExaminer-John McQuade enmar Attorney, Agent, or Firm-Browne, Beveridge,[73] Assignee: A. Jespersen & Son International DeGrand' & Klme A/S,Copenhagen, Denmark 221 Filed: Sept. 28, 1972 [57] ABSTRACT From US Pat.No. 3,642,419 it is known to pervey a [21] Appl' 293197 concrete castingmachine with more core tubes than necessary for a single mold. Thereforeat each casting [52] US. Cl 425/161, 425/ 162, 425/171, a number ofcore, tubes are retained, while the other 425/185, 425/468 core tubesare moved on a trolley towards and into the [51] Int. Cl. B28b 7/30empty mold. [58] Field of Search 425/457, 468, 182l86, Now the said coretubes are retained in their most 425/249! 4691 262; 249/631 177retracted position by means of twin-arm levers engaging either a fixhook in a link member connected [56] References C'ted to the core tube;this gives a reliable connecting and UNITED STATES PATENTS disconnectingpossibility which is vastly automatically 1,437,537 12/1922 Mazer425/468 controlled- 1,460,299 6/1923 Whitehouse 425/457 1,514,98011/1924 Mathis 425/468 21 Clam! D'awmg 44 37 -'E 64 11 14 1s 20 I 5 38WI i 30 23 925 1 1 l1 E i i g 35 in L i I1 "1. 1 7 1 11 11, 24 1 36 26 E11 I I 5 l HI22 111 43 *3 "M I r I||1|11 11111 1 "H 27 111 1 l 4)? 17 W1 1| ll ll m z J} J K PAIENTED N16 1 31974 SHEET '4 (IF 8 PAIENTED3.829.265

sum 8 [IF 8 The present invention relates to a device for connecting anddisconnecting core tubes connected to a trolley which inserts the tubesand retracts them from a concrete mold which serves for making castblocks or slabs. A similar trolley with core tubes is arranged at theopposite end of the mold.

U.S. Pat. No. 3,642,419 discloses a device for the said purpose, inwhich some of the core tubes of the casting machine, which are not to beused in the current production are permanently retained in theirretracted position. Each core tube in the known plant comprises a hingedswingable rear arm having a fastening device enabling the core tube tobe secured either to a fixed transverse beam or to the trolley, but saiddevice is for manual operation and will hardly lend itself to mechanicalswitching.

The object of the invention is to provide a mechanically switchabledevice to enable the'machine to be switched from one type of mold toanother type of mold from a control desk, either by hand orautomatically depending on the type of operation desired. Another objectof the invention is to provide a switching device which requires littlespace in width and height both during operation of the machine and whenconnecting and disconnecting core tubes. Thereby is achieved a compactmachine capable of accommodating a large number of core tubes, which isimportant as in such casting machines there are frequently used molds ofvarious width and shape. Now on one side it is frequently a question ofmolds requiring generally cylindrical cores, now on the other moldsrequiring cores of other cross section.

In such cases it is desirable to let the machine change automaticallybetween the two sets of core tubes.

The device according to the invention is so arranged that each tube isconnected through a link member with a twin-arm lever which by means ofhooks provided on the arms may alternately engage behind a fixed stopand in front of a projection provided on the trolley. Such a twin-armlever may not only be of a rugged construction so as to be capable oftransferring the necessary forces substantially appearing as tension inthe lever, but it also requires little space for its switching motion,and it further affords a high degree of protection against functionalerrors in the switching. Furthermore it may be constructed with suchsmall switching motion that rapid switching is possible, and to thisshould be added that it is possible to actuate the lever to effectswitching bysimple mechanical means, which may be controlledautomatically.

Said means may be designed so as to require little space, therebyallowingsuch a compact disposition of the core tubes that these may bearranged closely together in two or possibly more layers.

One embodiment of the device according to the invention is shown in thedrawings, in which FIG. 1 is a plan view of the rear end of some coretubes, in a casting machine, each of said core tubes being connected toits respective device for connecting and disconnecting the core tubes.

FIG. 2 is a sectional view taken on line A-A of FIG. 1 with core tube,disconnected from the trolley and connected to the fixed stop.

FIG. 3 is a perspective view of the lever of the device in the sameposition, as shown in FIG. 2.

FIG. 4 is a part sectional view corresponding to FIG. 2 after thetrolley is advancing again with the core tube disconnected.

FIG. 5 is a corresponding sectional view after the trolley has returnedand with the core tube connected thereto.

FIG. 6 is a perspective view of the lever in the same position as inFIG. 5.

FIGJ7 is a sectional view taken in line A-A of FIG. 1 after having movedthe trolley with the connected core tube a short distance away from theposition shown in FIG. 5.

FIG. 8 is a sectional view taken on line A-A of FIG. 1 after the trolleyhas returned with the core tube to its advanced end position, to whichit returns during operation when'no core tubes are to be connected ordisconnected.

FIG. 9 is a sectional view taken on line BB of FIG. 1 and FIG. 10 is adiagram of the automatical control devices.

In the drawings 11, 12, and 13 is illustrated the rear end of a numberof core tubes of the type designated 5 in U.S. Pat. No. 3,642,419. InFIG. 1 the rearend of each core tube is connected by a link pin 14through a rubber sleeve 15 to a link member 16 which is entered from therear into a horizontal U-shaped beam 17 on a trolley 18, one wheel 19 ofwhich is shown in FIGS. 1 and 9 on a rail 47.

The beam 17 is formed with a hole 20 which is sufficiently large to passover the core tube 11, see FIG. 2. The linkmember 16 has a U-shapedportion 21, FIG. 1 which is cut under an angle at the top and at thebottom so as to be able to engage the inclined surfaces within the beam17.

The rear end of the member 16,21 supports a tubular extension 23 havinga horizontal pin 24 to allow a tilting movement of a twin-arm lever 25.As willbe seen from FIG. 3, the lever may by means of a hook 26 providedthereon, engage a fixed stop 27, while the front of the lever supports across bar 28, the ends 29 of which may be guided behind a pair ofprojections 30 on the beam 17, FIGS. 1 and 2.

When the trolley is advanced towards the casting mold in the directionof arrow 31, the core tube 11,

shown in FIG. 2 will be immovably held as,a result of the engegement ofthe hook 26 behind the stop 27. FIG. 4 shows the trolley advancing inthe direction of the arrow 31, whereby the beam 17 with its hole 20 willpass over the core tube 11.

The trolley does, however, carry additional core tubes which areinserted into the casting mold, FIG. 10 and thereby forming'the desiredcores in the cast element. After the casting the trolley will retractsaid core tubes. Assuming mold of another type is to be cast in whichthe core 11 is to be used, the trolley is returned to its fullyretracted position shown in FIGS. 1 and 2. It is now required todisengage the hook 26- from the stop 27 and a cylinder 32, FIG. 5 isactuated to lift its piston rod 33 with pressure clamp 34, while turningcam 36 on shaft 35 clear of the lever 25. The latter is therebydepressed by a spring 38, located in the wall of housing 39 on themember 23 into the position shown' in FIG. 5, where the cross bar 28 ismoved down in front of the projections 30 on the beam 17 as shown inFIG. 6. The core tube 11 will thereby be disconnected from the stop 27and connected to the beam 17 and thus take part in the future movementsof the trolley 18.

It is common practice to have in such a casting machine two sets of coretubes, having different cross sections. It is then possible for themachine to operate with casting molds requiring core tubes either of onetype or the other. One could then have the cylinders 32 pressing theirclamps 34 against the levers of one set of core tubes when the secondset of core tubes is to be used and vice versa. It would, however, beeasier to provide two sets of cams 36 and 37 on the shaft 35. By turningthe shaft it is then possible to lock one or the other set of core tubesin the retracted position. On the other hand, the pressure clamps 34cannot be dispensed with as there at times are casting molds where oneor more core tubes of a set are to be used. In such case there coretubes are retained by actuating the associated cylinders 32, and bymeans of sensor, it will be possible automatically to adapt the choiceof core tubes to the mold introduced into the machine, as it will beexplained below.

FIG. 7 shows the beam 17 with core tubes 11 connected after the trolleyhas been moved a short distance away from its end position.

When the trolley returns and no changes in number of the core tubes 11,12, and 13 are to be made, because the next following operation requirescasting in a mold identical to the one just used, the trolley is notmoved back to the aforesaid fully retracted position, but to an advancedend position as shown in FIGS. 8 and 10. The buffer 46 of the trolley 18will not engage a fixed buffer 40 but a block 41, which meanwhile hasbeen lowered by a pressure cylinder 42 from position 41 indicated bydotted lines in FIG. 10.

It will be seen that the extended portion 23 of FIG. 8 may rest on arigidly mounted supporting roller 43. It will further be seen that whenmoved into the position shown in FIGS. 2 and 5, the member 23 will alsobe supported by an upper supporting roller 44, adjacent to the positionof the horizontal cross pin 24. Said supporting rollers 43 and 44 serveto support the entire link member during connection or disconnection ofthe core tubes 11, 12, 13 etc.

After a casting operation the trolley must always be returned to theadvanced end position, shown in FIG. 8. There is only a need for movingthe trolley 18 back to the fully retracted position, FIGS. 2 and 5, whenthe changing numbers or type is to take place.

Now the full mold is replaced by an empty mold 48 being introduced inthe direction of an arrow 49, FIG. 10.

If this mold is of a type B, i.e. of another type than the previous moldand lower, a sensor 52 on a shaft 51 which turns in a fixed bearing 68,will cause a lever 53 to actuate a limit switch 54, which lights a lamp54' on a panel 55, at the control desk of the machine. The limit switch54 will also actuate a solenoid valve 71, which gives a pressure fluidacces to the lower end of a cylinder 42, the stem 75 of which carriesthe block 41, which is now lifted up to the position 41 This will allowthe trolley to drive against the buffer 40, as explained below. The stem75 has a side bar 76 with a projection 77, which actuates a limit switch72, closing the solenoid valve 71, when the block has reached its upperposition 41 The limit switch 72 closes a contact 78 which causes a slowmovement of the trolley 18 backwards against the buffer 40, in whichposition the guide bracket 56 on the trolley 18 will actuate a limitswitch 60 which actuates a solenoid valve 70, which opens for admissionof pressure fluid to the right end of the cylinder, FIG. 10, which issupported turnable on a pin 62, on a rigid arm 63 on the beam 64.Thereby the stem 79 of the cylinder 61 pushes through a pin 80 against aL-shaped lever 67 on a shaft 35 which is thereby turned. The shaft 35has two sets of cams 36 and 37. When turning, the earns 37 are presseddown on the levers 25, locking them in engagement with the stops 27 andat the same time the front end of the levers will disengage theprojections 30, FIG. 3. Thereby the core tubes, which should be appliedin connection with molds of type A will be retained, when the trolley 18is driven forwards. Oppositely will the core tubes which have beenhitherto retained be released from the stops 27 and connected to thetrolley 18, because the corresponding cams 36 will release thecorresponding levers 25, which will thereby be tilted by their springdevice 39 from the position shown in FIG. 6.

The piston stem 79 carries a side bar 81, having a projection 82. Thisprojection contacts a limit'switch 83, and the movement is stopped,because the switch will close valve 70. When later on the core tubes aresubstituted by the other set of tubes, the signal from limit'switch 60will cause the valve 70 to admit pressurized fluid to the left end ofthe cylinder, cf. FIG. 10.

Hereby the shaft 35 is turned back to the position shown in FIG. 10,said movement being stopped as the projection 82 contacts a limit switch84 which closes the valve 70.

The cams 36 and 37 of shaft 35 will either retain the core tubes to thetype A-molds or the core types to the B-molds.

Each of said twin-armed levers 25 will as the hook 26 thereof engageswith the corresponding stop 27, actuate limit switch 45 which lights alamp 45' of the panel 55. Hereby it is possible to ascertain those coretubes that are retracted.

By actuation of a switch 85 the trolley 18 is connected to the powersupply. The trolley moves then forwards in the direction of the typeB-mold 48 and the corresponding core tubes into the mold through theopenings 87 of the end-wall 50. As the guide bracket.

56 during this procedure passes the limit switch 86, the latter willproduce a signal for the valve 71. Hereby the valve is opened forpressure to the upper end of the cylinder 42, which involves that theblock 41 is moved down to position 41 of FIG. 10, in which position itwill stop because the projection 77 contacts limit switch 73 whichcloses valve 71.

If the empty mold 48 is of type A, a second limit switch 59, workingwith the lever 53, will be actuated, whereby a lamp 59 on the panel islighted. In this case no changing of core tubes will be made. The block41 will not be lifted, because the trolley 18 will not be moved beyondthe position shown in FIGS. 8 and 10. No signal is given to the valve70, because it is the same limit switch 59 which is actuated as at theprevious mold. The limit switch 59 actuates a relay 90, but may nottransfer its signal to the valve 71, because the relay already by anearlier signal has moved a switch 89 to the position shown in FIG. 10.When the lever 53 passed limit switch 54 on its way to or from limitswitch 59 a time delay-relay 94 inserted in the circuit to the switch 89will prevent an impulse from passing until say 3 seconds have elapsed.

By manual operation of the switch 89 it is possible if desired to movethe trolley 18 back to the retracted position. If no simultanous turningof the shaft 35 is desired, a switch 91, inserted in the connection 92passing from valve 71 to the valve 70, is opened. This is necessary if amold which differs somewhat from the two mold types is to be cast. Asingle, some or all of the core tubes, not held by the cams 36 or 37 maybe retained by means of the pressure clamps 34 mentioned above. Eachpressure cylinder 32 may be actuated by pressing its particular pressbutton 32 on the panel 55, whereby the corresponding lamp 45 is lighted.All of the buttons 32' may be released by pressing a re-set button 132,whereby all clamps 34 are lifted, thereby freeing the hooks 26.

What I claim is:

1. In a concrete block and slab molding apparatus including a pluralityof core tubes having a forward end adapted to be projected into a moldat a mold station and a rear end, a trolley movable on a track towardand away from a mold at said molding station between an extendedposition in which said core tubes project into the mold at said moldstation and a fully retracted position in which said core tubes arewithdrawn from said molds,and connecting means operable to selectivelyconnect the rear end of said core tubes to said trolley for movementtherewith and to connect said tubes to a stationary support when saidtrolley is in said fully retracted position, the improvement whereinsaid connecting means comprises a linkage assembly on each said coretube, said linkage assemblies each including an elongated link memberhaving one end connected to the rear end of a core tube, a leverpivotally mounted on said link for movement between a first position anda second position, first and second hook means on said lever, fixed stopmeans adapted to be engaged by said first hook means when said lever isin said first position to retain the core tube against movement withsaid trolley, and projection means on said trolley adapted to be engagedby said second hook means when said lever is in said second position toconnect said core tube to said trolley for movement therewith.

2. The molding apparatus according to claim 1 wherein said connectingmeans further comprises a spring member located between said lever andsaid link and normally urging said lever away from said first positionand out of engagement with said fixed stop.

3. The molding apparatus according to claim 2 further comprising amovable member located adjacent said fixed stop and adapted to pressagainst said lever in the area of said hook to cause the latter toengage said fixed stop and disengage from said projection on saidtrolley when said core tube is to be connected to said fixed support.

4. The molding apparatus according to claim 1 wherein said second hookmeans comprises a cross bar mounted on and having its ends projectinglaterally from said lever for engaging said projection means on saidtrolley on each side of said lever.

5. The molding apparatus according to claim 4 wherein said trolleyincludes a beam extending generally transverse to the direction ofmovement of the trolley, said link having two outer surfaces inclinedtoward each other in the direction of said core tube and said beamhaving complementary inclined inner surfaces positioned to engage andsupport said inclined surfaces on said link when said second hook is insaid second position connecting said core tube to said trolley, saidprojection means also being located on and supported by said beam inposition to be engaged by said cross bar.

6. The molding apparatus as defined in claim 1 further comprisingmovable stop means for engaging and stopping movement of said trolley ata partially retracted position in which the core tubes carried thereonare withdrawn from a mold at said molding station and in which thelinkage assembly on the core tubes connected to said trolley are spacedfrom said stationary support whereby the trolley is prevented frommovement to said fully retracted position when it is not desired tochange the core tube configuration carried thereby, and means for movingsaid stop means to permit the trolley to move to said fully retractedposition when it is desired to change the core tube configurationcarried thereby.

7. The molding apparatus according to claim 6 wherein said linkscomprise an elongated tubular member extending rearwardly from said coretube, said lever being pivotally mounted within said tubular member formovement about a horizontal axis, and guide roll means positionedbeneath and engaging a first guide surface on said tubular member forguiding said linkage assembly during movement of said trolley betweensaid partially retracted position and said fully retracted position.

8. The molding apparatus according to claim 7 wherein said spring memberis located within said tubular member.

9. The molding apparatus according to claim 7 wherein said tubularmember includes a second guide surfaceextending along the top portionthereof adjacent its rear end, and a supporting roller mounted in fixedbearings in position to engage said second guide surface as said trolleyand said core tubes are moved between said fully retracted position andsaid partially retracted position.

10. The molding apparatus according to claim 3 further comprising anelongated cam shaft extending across all of said levers at said fullyretracted position, cams mounted on said cam shaft in position to engagesaid levers, and means for rotating said shaft to engage said cams withsaid levers to press the hooks there into engagement with thecorresponding fixed stops.

11. The molding apparatus according to claim 10 further comprising twosets of core tubes adapted to be selectively connected to said trolleyfor movement therewith, and wherein said cams on said shaft include twosets of cams each adapted to engage the levers of one set of said coretubes, said shaft being rotatable between positions alternativelyconnecting one or the other of said sets of core tubes to said trolleyfor movement therewith.

12.-The molding apparatus according to claim 11 wherein said means forrotating said cam shaft includes an arm and a fluid cylinder operable tooscillate said arm and said cam shaft about the longitudinal axis ofsaid shaft.

13. The molding apparatus according to claim 12 further comprising asolenoid actuated valve operatively connected in a fluid circuitcontrolling operation of said first fluid cylinder, and meanscontrolling actuation of said solenoid valve to rotate said cam shaft topress either one or the other of said sets of cams against theirassociated levers to thereby connect the core tubes to said stationarysupport.

14. The molding apparatus according to claim 1 further comprising afirst limit switch mounted in position to be actuated by each saidlever, and a plurality of lamps on a control panel connected one to eachsaid limit switch for signaling when the respective levers have theirhooks connected with said fixed stops.

15. The molding apparatus as claimed in claim 1 further comprising clampmeans mounted adjacent each said lever at said fully retracted positionfor clamping the lever to its fixed stop.

16. The molding apparatus as claimed in claim wherein said clamp meanscomprises a piston rod of a fluid pressure cylinder, said fluid pressurecylinder being operable to maintain the hook on the associated lever inengagement with said fixed stop regardless of the position of said camshaft.

17. The molding apparatus as claimed in claim 9 further comprising astationary buffer for stopping movement of said trolley at said fullyretracted position, said movable stop including a block adaptable to bemoved into position to engage said trolley ahead of said stationarybuffer whereby said trolley may be stopped in said partially retractedposition.

18. The molding apparatus as claimed in claim 17 wherein said molds aremoved seriatim past said molding station, sensor means mounted inposition to engage said molds at said molding station, and meansresponsive to said sensor means for moving said block in response to acondition sensed by said sensor means.

19. The molding apparatus as claimed in claim 18 wherein said sensormeans comprises a pair of limit switches mounted in position to beactuated depending upon the height of the molds moved into said moldingstation for sensing a change in mold size and for producing a signalcontrolling movement of said block from its normal position ahead ofsaid buffer at said first actuation of a limit switch after a change ofmold size.

20. The molding apparatus as claimed in claim 12 further comprising afurther limit switch mounted in position to be actuated-by said coretube carrying trolley when said trolley is in said fully retractedposition, said furtherlimit switch being connected in a circuitincluding a signal lamp on said control panel and a solenoid actuatedvalve operably connected to said first fluid cylinder for rotating saidcam shaft whereby said shaft is turned upon movement of said trolley tosaid fully retracted position.

21. The molding apparatus as claimed in claim 17 further comprisingswitch means mounted for actuation by movement of said trolley towardsaid fully retracted position and operably connected to said means formoving said movable block whereby said block is moved away from saidfixed buffer.

1. In a concrete block and slab molding apparatus including a pluralityof core tubes having a forward end adapted to be projected into a moldat a mold station and a rear end, a trolley movable on a track towardand away from a mold at said molding Station between an extendedposition in which said core tubes project into the mold at said moldstation and a fully retracted position in which said core tubes arewithdrawn from said molds, and connecting means operable to selectivelyconnect the rear end of said core tubes to said trolley for movementtherewith and to connect said tubes to a stationary support when saidtrolley is in said fully retracted position, the improvement whereinsaid connecting means comprises a linkage assembly on each said coretube, said linkage assemblies each including an elongated link memberhaving one end connected to the rear end of a core tube, a leverpivotally mounted on said link for movement between a first position anda second position, first and second hook means on said lever, fixed stopmeans adapted to be engaged by said first hook means when said lever isin said first position to retain the core tube against movement withsaid trolley, and projection means on said trolley adapted to be engagedby said second hook means when said lever is in said second position toconnect said core tube to said trolley for movement therewith.
 2. Themolding apparatus according to claim 1 wherein said connecting meansfurther comprises a spring member located between said lever and saidlink and normally urging said lever away from said first position andout of engagement with said fixed stop.
 3. The molding apparatusaccording to claim 2 further comprising a movable member locatedadjacent said fixed stop and adapted to press against said lever in thearea of said hook to cause the latter to engage said fixed stop anddisengage from said projection on said trolley when said core tube is tobe connected to said fixed support.
 4. The molding apparatus accordingto claim 1 wherein said second hook means comprises a cross bar mountedon and having its ends projecting laterally from said lever for engagingsaid projection means on said trolley on each side of said lever.
 5. Themolding apparatus according to claim 4 wherein said trolley includes abeam extending generally transverse to the direction of movement of thetrolley, said link having two outer surfaces inclined toward each otherin the direction of said core tube and said beam having complementaryinclined inner surfaces positioned to engage and support said inclinedsurfaces on said link when said second hook is in said second positionconnecting said core tube to said trolley, said projection means alsobeing located on and supported by said beam in position to be engaged bysaid cross bar.
 6. The molding apparatus as defined in claim 1 furthercomprising movable stop means for engaging and stopping movement of saidtrolley at a partially retracted position in which the core tubescarried thereon are withdrawn from a mold at said molding station and inwhich the linkage assembly on the core tubes connected to said trolleyare spaced from said stationary support whereby the trolley is preventedfrom movement to said fully retracted position when it is not desired tochange the core tube configuration carried thereby, and means for movingsaid stop means to permit the trolley to move to said fully retractedposition when it is desired to change the core tube configurationcarried thereby.
 7. The molding apparatus according to claim 6 whereinsaid links comprise an elongated tubular member extending rearwardlyfrom said core tube, said lever being pivotally mounted within saidtubular member for movement about a horizontal axis, and guide rollmeans positioned beneath and engaging a first guide surface on saidtubular member for guiding said linkage assembly during movement of saidtrolley between said partially retracted position and said fullyretracted position.
 8. The molding apparatus according to claim 7wherein said spring member is located within said tubular member.
 9. Themolding apparatus according to claim 7 wherein said tubular memberincludes a second guide surface extending along the top portion thEreofadjacent its rear end, and a supporting roller mounted in fixed bearingsin position to engage said second guide surface as said trolley and saidcore tubes are moved between said fully retracted position and saidpartially retracted position.
 10. The molding apparatus according toclaim 3 further comprising an elongated cam shaft extending across allof said levers at said fully retracted position, cams mounted on saidcam shaft in position to engage said levers, and means for rotating saidshaft to engage said cams with said levers to press the hooks there intoengagement with the corresponding fixed stops.
 11. The molding apparatusaccording to claim 10 further comprising two sets of core tubes adaptedto be selectively connected to said trolley for movement therewith, andwherein said cams on said shaft include two sets of cams each adapted toengage the levers of one set of said core tubes, said shaft beingrotatable between positions alternatively connecting one or the other ofsaid sets of core tubes to said trolley for movement therewith.
 12. Themolding apparatus according to claim 11 wherein said means for rotatingsaid cam shaft includes an arm and a fluid cylinder operable tooscillate said arm and said cam shaft about the longitudinal axis ofsaid shaft.
 13. The molding apparatus according to claim 12 furthercomprising a solenoid actuated valve operatively connected in a fluidcircuit controlling operation of said first fluid cylinder, and meanscontrolling actuation of said solenoid valve to rotate said cam shaft topress either one or the other of said sets of cams against theirassociated levers to thereby connect the core tubes to said stationarysupport.
 14. The molding apparatus according to claim 1 furthercomprising a first limit switch mounted in position to be actuated byeach said lever, and a plurality of lamps on a control panel connectedone to each said limit switch for signaling when the respective levershave their hooks connected with said fixed stops.
 15. The moldingapparatus as claimed in claim 1 further comprising clamp means mountedadjacent each said lever at said fully retracted position for clampingthe lever to its fixed stop.
 16. The molding apparatus as claimed inclaim 15 wherein said clamp means comprises a piston rod of a fluidpressure cylinder, said fluid pressure cylinder being operable tomaintain the hook on the associated lever in engagement with said fixedstop regardless of the position of said cam shaft.
 17. The moldingapparatus as claimed in claim 9 further comprising a stationary bufferfor stopping movement of said trolley at said fully retracted position,said movable stop including a block adaptable to be moved into positionto engage said trolley ahead of said stationary buffer whereby saidtrolley may be stopped in said partially retracted position.
 18. Themolding apparatus as claimed in claim 17 wherein said molds are movedseriatim past said molding station, sensor means mounted in position toengage said molds at said molding station, and means responsive to saidsensor means for moving said block in response to a condition sensed bysaid sensor means.
 19. The molding apparatus as claimed in claim 18wherein said sensor means comprises a pair of limit switches mounted inposition to be actuated depending upon the height of the molds movedinto said molding station for sensing a change in mold size and forproducing a signal controlling movement of said block from its normalposition ahead of said buffer at said first actuation of a limit switchafter a change of mold size.
 20. The molding apparatus as claimed inclaim 12 further comprising a further limit switch mounted in positionto be actuated by said core tube carrying trolley when said trolley isin said fully retracted position, said further limit switch beingconnected in a circuit including a signal lamp on said control panel anda solenoid actuated valve operably connected to said first fluidcylinder for rotatiNg said cam shaft whereby said shaft is turned uponmovement of said trolley to said fully retracted position.
 21. Themolding apparatus as claimed in claim 17 further comprising switch meansmounted for actuation by movement of said trolley toward said fullyretracted position and operably connected to said means for moving saidmovable block whereby said block is moved away from said fixed buffer.